Octane requirements for the 6.4 Hemi???

[Pronto]

I downloaded the 2020 2500 manual and can verify that it is as Sdoctor86 posted. There is no longer a mention of 89 octane. Here is the full passage on octane cut and pasted from the 2020 manual:

FUEL REQUIREMENTS — GAS ENGINE
6.4L ENGINE
Do not use E-85 flex fuel or ethanol blends
greater than 15% in this engine.
This engine is designed to meet all
emissions regulations and provide
satisfactory fuel economy and
performance when using high quality
unleaded gasoline having a posted octane
number range of 87 as specified by the
(R+M)/2 method.
While operating on gasoline with an octane
number of 87, hearing a light knocking sound
from the engine is not a cause for concern.
However, if the engine is heard making a heavy
knocking sound, see dealer immediately. Use of
gasoline with an octane number lower than 87
can cause engine failure and may void or not be
covered by the New Vehicle Limited Warranty.
Poor quality gasoline can cause problems such
as hard starting, stalling, and hesitations. If you
experience these symptoms, try another brand
of gasoline before considering service for the
vehicle

 

[Squatch]

That is definitely not what it said in 2019 manual, at least not that I can remember. Wonder what they found out, or what changed? I accidentally put lowest grade in it last time I filled up, I noticed no difference at all, but I do add the lucas injector cleaner and fuel conditioner (maybe snake oil) at every fill up, so maybe that has some effect. Who knows...

 

[Pronto]

I bet nothing changed other than some focus group analysis. They probably figured that the mileage and performance gain was negligible but that some potential buyers were being lost by the higher octane recommendation. I'm glad they changed it. I honestly can't tell a difference between 87 and 89 in my 5.7 Hemi but I still pump 89 just because of the recommendation. My new 6.4 will be getting 87 only and I won't worry about it.

 

[louisiana_dog]

My 2020 states 89 is recommended and the 87 is ok as mentioned above. Though I do have an 89 stamp next to the paragraph. I'll use ethanol in car engines as they can handle it these days and the gas doesn't sit and have a chance to eat away.

However, my generator, chainsaws, and other small engines get non-ethanol...I run the saws once a week and the generator once a month. I hate saws that sit up and hate old gas, so the best thing is to just run them for a minute or two if not using them. You can drain the fuel, but if you're like me and using a saw once or twice a month or so, it is easier to just run the thing.

 

[oaklandopen]

Could octane recommendation have anything to do with the MDS? I'm guessing with half the cylinders activated pushing the same 7,000 lbs the risk of knock increases until it goes back to V8 mode

 

[jsalbre]

Both the paper manual in my 2020 truck, the manual I had downloaded, and the one I just pulled from mopar.com list 89 recommended, 87 required, with an increased risk of knock on 87. The little graphic on all 3 shows 89.

I do run 87 at altitude (5000’+) but change back to 89 when I’m headed back out of the mountains.

 

[dtsequeira]

I've only put 87 in mine since new. I live at sea level and camp above 10k multiple times a year carrying our camper and have never noticed it knocking on 87.

 

[jsalbre]

I've only put 87 in mine since new. I live at sea level and camp above 10k multiple times a year carrying our camper and have never noticed it knocking on 87.

With the active noise cancellation and all the insulation in our trucks you probably wouldn’t notice minor knocking.

 

[Firebird]

50% of my miles are towing miles, so I run 89 all the time.

 

[Sdoctor86]

One overlooked aspect of gasoline is the detergent blend the gas station uses. Every gas station has a special blend, and some are rated as top tier for reaching a certain level of quality. Detergent is important for extending the performance and life of your engine by preventing buildup.

https://en.m.wikipedia.org/wiki/Top_Tier_Detergent_Gasoline

 

[Pronto]

Both the paper manual in my 2020 truck, the manual I had downloaded, and the one I just pulled from mopar.com list 89 recommended, 87 required, with an increased risk of knock on 87. The little graphic on all 3 shows 89.

I do run 87 at altitude (5000’+) but change back to 89 when I’m headed back out of the mountains.

That's weird, the one I downloaded from there on Nov 25 had no mention of 89. I just tried to recheck and it never loads the page when I click on Ram in the menu selection.

 

[Spedly]

I run 87 all the time I’ve had no audible spark knock when towing our 11klb trailer. I tried 89 one time towing and it made no difference. Putting 91 or 93 in these trucks would be a waste of money.

 

[desert_wagon]

91 and done, the cost is minimal compared to the initial investment.

 

[Team Ramrod]

I ran nothing but 93 in my previous 2016 Mega Cab 6.4 and wont make the same mistake twice. Unfortunately I didnt take the time to educate myself and needlessly spent a ton of extra money on fuel. I will run 89 in this new truck exclusively.

 

[Pronto]

I just checked the printed manual that came with my 2021 2500 Hemi that I picked up yesterday. The section on octane is the same as in the downloaded manual that I posted earlier in this thread. It recommends 87 period, there is no mention of 89 or any other octane level at all.

 

[Gondul]

Straight out of my 2019 manual.... <shrug>

 

[Pronto]

Yep, it's been that on the Hemi's up to this year but for 2021 6.4, it's now just 87. Don't know if they did the same to the 5.7.

 

[jadmt]

my 2020 owners manual says 87 and no mention of 89. Page 471.

6.4L ENGINE
Do not use E-85 flex fuel or ethanol blends
greater than 15% in this engine.
This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality
unleaded gasoline having a posted octane number range of 87 as specified by the (R+M)/2 method.
While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see dealer immediately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty.

 

[Pronto]

Ok, I was thinking it was new for this year but I guess it happened last year.

 

[louisiana_dog]

I wonder when they switched. Maybe the manufacturing date determined when they switched over to 87. Mine was made in July and recommends 89.